A project consists of five activities as shown in the following table. Activity Optimistic Time (hr) Most Probable Time (hr) Pessimistic Time (hr) Floor sanding 4 5 6 Floor buffing 3 4 5 Paint mixing 0.5 1 1.5 Wall painting 3 4 11 Ceiling painting 3 7.5 9 Naturally, the paint mixing precedes the painting activities. Also, both ceiling painting and floor sanding must be done prior to floor buffing. (a) Construct the PERT/CPM network for this problem. Floor Floor Floor Floor Sanding Sanding Buffing Buffing Paint Paint Start Finish Start Finish Wall Ceiling paint Paint Mixing Mixing Paint Paint Wall Ceiling O DO A C Floor Floor Floor Floor Sanding Buffing Buffing Sanding Paint Paint Finish Start Finish Start Wall Ceiling Paint Paint Mixing Mixing Paint Paint Wall Ceiling DO D(b) What is the expected completion time (in hours) of this project? hr (c) What is the probability that the project can be completed within thirteen hours? (Round your answer to four decimal places.)